Manufacture of incandescent lamps.



E. LAMBERT.

MANUFACTURE OF INGANDESOENT LAMPS. APPLICATION FILED FEB.1,1912.

1,1 20,064, Patented Dec. 8, 1914.

g I Z I VENT R ATTORNEY UNITED STATES PATENT OFFICE.

EDNA LAMBERT, 0F JERSEY CITY, NEXV JERSEY, ASSIGNOR T0 WESTINGHOUSE LAMP COMPANY, A CORPORATION OF PENNSYLVANIA.

MANUFACTURE OF INCANDESCENT LAMPS.

Specification of Letters Patent.

Patented Dec. 8, 1914.

Application filed February 1, 1912, Serial No. 674,804.

To alt whom it may roaocrn:

lie it known that I, EDNA LAMBERT, a citizen of the United States, and a resident of Jersey City, in the county of Hudson and State of New Jersey, have invented a new and useful Improvement in the Manufacture of Incandescent Lamps, of which the following is a specification.

My invention relates to the manufacture of electric incandescent lamps, and particularly to the process known as sealing in, which consists in joining theflared ends of the filament carriers or stems to the base ends of the inclosing bulbs.

Sealing-in, as heretofore practised, usually consisted in first removing the superfluous portion of the neck of a lamp bulb by heating the stem at a predetermined place, until the glass became so softened that the superfluous portion dropped off by reason of its own weight. \Vhile the glass at the neck was still soft, the operator blew into the bulb from the opposite end to cause the formation of a bubble which was immediately broken and removed, leaving the end of the neck of a somewhat conical form corresponding to the flare of the lower end of the stem constituting part of the filament support. The bulb, as thus prepared, was then slipped over the filament support, and the lower ends of the bulb and stem were melted togethed in a blow-pipe flame. This process outlined above is very successful and satisfactory when the filament systems are of comparatively small diameter, so that the necks of the bulbs may be of correspondingly small diameter, and will, therefore, require but a comparatively small amount of reduction preparatory to the final step of the sealing-in process. However, when the filament systems are of comparatively large diameter, such, for instance, as those of the modern metal filament lamps, the.

necks of the bulbs are necessarily correspondingly large in diameter, and much difliculty has been experienced in reducing them sufficiently for joining to the flared ends of the stems. These difficulties arise from the fact that the quantity of glass in the large bulb neck is so great that, when the neck is melted down upon the stem, the glass is subjected to undue internal stresses, and the seal or joint frequently cracks upon cooling, and thus entails a practically prohibitive loss in manufacturing.

Various means have heretofore been suggested and employed for overcoming the diiliculties above set forth, involving the use of complicated and expensive machines for performing the desired and necessary operations.

According to the present invention, the sealing-in operation may be eli'ected expeditiously by the use of a comparatively simple machine, while the thickness of the glass in the neck adjacent to the seal between the bulb and the stem is substantially the same as in other portions of the bulb, with the result that the internal stresses are not ex cessive, and the loss in manufacture is very materially reduced.

Figure 1 of the accompanying drawing shows a bulb that has been slipped over the stem and filament system preparatory to the first step of the operation. Fig. 2 shows a machine-by means of which the present process may be practised, the lamp parts being shown in the next step of the operation, and Fig. 3 illustrates a completed lamp.

In practising the present invention, the superfluous portion of the neck of a bulb 1 is first removed in the ordinary manner as described above, a smaller portion of it, however, being removed than has heretofore been customary. A lamp stem 2 carrying the supports upon which the filament is mounted is then placed upon the upper end of a vertical supporting rod 3, and the bulb is slipped over the same, so that the parts bear the relations shown in Fig. 1. The bulb is supported by a ring 4 constituting part of a rotatable frame 5 that is carried by a vertical shaft 6 upon which is mounted a gear wheel 7 that meshes with a driving pinion 8 for effecting rotation thereof. The pinion is of somewhat greater axial length than the gear to permit of a slight amount of vertical reciprocation of the rotatable frame, which may be effected by means of a lever 9 having an operative connection with the lower end of the shaft 6. Heat is then applied to the bulb about '1; or of an inch above the flared lower end of the stem, by means of the flames from blow pipes 10, the bulb being rotated during this application of heat. When the glass has become suiticiently softened, the lower end of the neck of the bulb is drawn downwardly to elongate the heated and softened portion thereof, and to cause the same to contract around the flared end of the stem, the application of heat being discontinued during the drawing operation. The bulb then has substantially the shape shown in Fig. 2, and the contracted portion thereof engages, or is closely adjacent to, the flared end of the stem. ll he blow-pipe flames are then again directed upon the bulb at a short distance above the lower end of the stem, and the frame carrying both the stem and the bulb, is then gradually moved upwardly so that heat will be applied to the bulb progressively from a point a short distance above the lower end of the stem to point adjacent to the lower end of the stem where the application of heat is continued for a sufficient period to melt or seal together the bulb and the stem. The flames are then directed upon the neck of the bulb at a point just below the junction thus effected between the bulb and the stem, in order to melt off the superfluous portion of the neck, which becomes severed by its own weight. .Jhe united portions are then heated until they have softened somewhat, and with the lamp removed from the supporting frame the stem is drawn outwardly by means of a pair of tweezers until the bulb has assumed the proper and desired.

shape. The small end of the bulb is then of such shape and size as to permit of the application thereto of the ordinary and standard lamp base, the finished lamp appearing as shown. in Fig. 8. Since the neck of the bulb is elongated at the same that it is contracted around the flared end of the stem, the thickness of the glass is reduced so that the glass adjacent to th completed joint is no thicker than in other portions of the bulb, and, accordingly, 'is not subjected to undue internal strains. The

result is that the brealrage from this cause is negli ible and that the lamps are highly satisfactory in service.

I claim as my invention:

1. The process of joining a lamp bulb to a filament support or stem which consists in heating and softening the bulb in a circular zone a short distance from the end of the stem, elongating and contracting the softencd portion thereof, progressively reheating the bulb from a short distance from the end of the stem to a point opposite the same, and sealing the bulb to the stem.

2. lhe process of joining a lamp bulb to a filament support or stem which consists in heating and softening the bulb in a circular zone somewhat above the lower end of the stem, pulling the lower end of the bulb downwardlyto elongate the softened portion thereof and contract it about the of the stem, then progressively'reheating the bulb from above the lower end of the stem downwardly, joining the bulb to the lower end of the stem, and removing the superfluous part of the bulb.

3. "l he process of joining a lamp bulb to a filament support or stem which consists in heating and softening the bulb in a circular zone somewhat above the lower end of the stem, pulling the lower end of the bulb dow wardly to elongate the softened por tion thereof and contract it about the end of the stem, then progressively reheating the bulb from above the lower end of the stem downwardly, and joining the bulb the lower end of the stem V In testimony whereof, I have hereunto subscribed my name this 16th day of January 1912i -EDNA LAMBERT.

Witnesses: W

()HARLES BZELLY, O'rro S. Scnanann, 

